Information
-
Patent Grant
-
6412763
-
Patent Number
6,412,763
-
Date Filed
Thursday, October 12, 200024 years ago
-
Date Issued
Tuesday, July 2, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 269 20
- 269 24
- 269 32
- 269 25
- 254 93 H
- 029 252
-
International Classifications
-
Abstract
A rotary cylinder actuator has a piston rod placed in a cylinder, provided in its surface with a guide groove and capable of being moved axially between a position corresponding to a clamping angular position and a position corresponding to an unclamping angular position. A guide member is attached to the cylinder to engage in the guide groove. The piston rod turns from a first angular end position toward a second angular end position for normal turning and turns from the second angular end position toward the first angular end position for reverse turning. The opposite guide surfaces of the guide groove serve as a first guide surface for normal turning and a second guide surface for reverse turning, respectively, so that the guide member moves relative to the piston along different paths in the guide groove while the piston rod turns for normal turning and reverse turning, respectively. The first guide surface and the second guide surface are formed so that the guide member moves relative to the piston rod along a path having a shape of a section of a sine curve or a cosine curve in a final stage of movement of the piston rod, and the guide member moves relative to the piston rod so as not to produce any torque at the second angular end position.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary clamping cylinder actuator having a clamping arm attached to the free end of a piston rod connected to a piston of a hydraulic cylinder actuator and capable of turning the clamping arm between a clamping position in front of a workpiece and an unclamping position apart from the workpiece.
2. Description of the Related Art
A known clamping cylinder actuator shown in FIG. 1 of JP-B-62-5739 has a piston rod provided in its outer surface with a guide groove consisting of a helical guide section extended oblique to the axis thereof and a straight guide section continuous with the helical guide section and corresponding to a clamping angular position, and a guide member, such as a guide pin, connected to an end cover and slidably engaged with the guide groove. When a piston fitted in the cylinder bore of a cylinder and connected to the piston rod is advanced from its back end position, a clamping arm connected to the extremity of the piston rod and positioned at a clamping angular position in front of a workpiece is moved linearly away from the workpiece while the straight guide section of the guide groove moves relative to the guide member. As the piston rod is advanced further, the helical guide section of the guide groove moves relative to the guide member and thereby the clamping arm is turned to an unclamping angular position separated from the workpiece.
The unclamping angular position is determined by the position of the guide member relative to the helical guide section of the guide groove and hence the unclamping angular position is dependent on the stroke of the piston. Therefore, the clamping arm cannot be turned accurately through a predetermined angle and the clamping arm cannot be accurately turned to the unclamping angular position unless the component parts of the clamping cylinder actuator are managed properly to determine the stroke of the piston accurately. When the clamping arm clamping a workpiece is moved from the clamping angular position to the unclamping angular position, the extremity of the helical guide section comes into contact with the guide member and the inertial force of the turning clamping arm exerts intensive shocks on the guide member and the helical guide section of the guide groove, which causes the abrasion of the guide member and a portion of the piston rod corresponding to the extremity of the helical guide section and shortens the life of the clamping cylinder actuator.
When the guide member in engagement with the helical guide section comes into engagement with the straight guide section of the guide groove corresponding to the clamping angular position, the clamping arm, hence the piston rod, stops at the clamping angular position. However, it is not clear whether or not the clamping arm can be stopped accurately at the clamping angular position without exerting intensive shocks on the guide member.
Since the piston rod turns together with the piston, a sealing member (packing ring) fitted around the piston to seal the gap between the piston and the cylinder wall defining the cylinder bore exerts a resistance to the turning of the piston rod. The effect of this resistance is determined by friction between the sealing member and the cylinder wall, and the inside diameter of the cylinder bore. Therefore, the clamping arm cannot be turned unless an axial pressure high enough to turn the piston against the effect of the resistance is applied to the piston.
Accordingly, it is an object of the present invention to provide a rotary clamping cylinder actuator capable of turning a clamping arm through a fixed angle even if the stroke of a piston included therein is not controlled accurately and of reducing the effect of the inertial force of the clamping arm when stopping the clamping arm at an unclamping angular position.
A second object of the present invention is to provide an interlocking mechanism that exerts less resistance to the relative movement of interlocked members than the sliding guide mechanism interlocking a guide groove and a guide pin.
A third object of the present invention is to provide a rod turning mechanism having a rotary rod holding a turning member, such as a clamping arm, and capable of reducing the inertial force of the turning member at the opposite terminal ends of turning motion of the turning member to stop the turning member gradually and of starting turning the turning member at a high turning speed.
A fourth object of the present invention is to provide a rotary clamping cylinder actuator having a rotary member capable of turning under a low resistance and without requiring a high working pressure.
SUMMARY OF THE INVENTION
According to the present invention, a rotary clamping cylinder actuator comprises: a cylinder; a piston provided in the cylinder; a front end cover attached to a front end of the cylinder; a rotatable piston rod provided in an outer surface thereof with a guide groove and contained in the cylinder so as to project to outside through the front end cover and capable of rotating about its axis; a guide member attached to one of the cylinder and the piston and engaged in the guide groove of the piston rod so as to be movable relative to the piston rod in directions parallel to the axis of the piston rod; and a clamping arm attached to a free end of the piston rod and capable of being turned together with the piston rod between a clamping angular position and an unclamping angular position; wherein the guide groove has an oblique guide section extending oblique to the axis of the piston rod to turn the piston rod, a first straight guide section connected to one end of the oblique guide section and corresponding to the clamping angular position, and a second straight guide section connected to the other end of the oblique guide section and corresponding to the unclamping angular position, and the oblique guide section and the second straight guide section are so connected that the center of the guide member moves substantially along a circular arc when the guide member moves relative to the piston rod from the oblique guide section to the second straight guide section corresponding to the unclamping angular position.
Since the center of the guide member moves along the circular arc when the guide member moves from the oblique guide section to the second straight guide section corresponding to the unclamping angular position, the guide member is able to move very smoothly relative to the piston rod. Since the piston rod stops after moving straight instead of suddenly stopping while the same is turning, the rotational inertial force of the turning clamping arm can be reduced before the clamping arm stops at the unclamping angular position. Since the angular interval between the two stopping angular positions of the piston rod (hence the clamping arm) is dependent on the angular interval between the first and the second straight guide section, the stroke of the piston does not need to be controlled accurately and the angular interval between the two stopping angular positions can be accurately determined by properly machining the piston rod.
Preferably, the oblique guide section and the second straight guide section corresponding to the unclamping angular position of the guide groove are connected by an arcuate connecting section having the shape of a circular arc, a clamping guide surface of the oblique guide section that engages the guide member when the piston rod is thrust by a piston, and one guide surface of the second straight guide section corresponding to the unclamping angular position are connected by an arcuate connecting surface, and the center of the guide member moves along a circular arc when the guide member is guided by the arcuate connecting surface in the arcuate connecting section.
Preferably, in the arcuate connecting section, an unclamping guide surface of the oblique guide section that engages the guide member when the piston rod is thrust by a piston toward the unclamping angular position, and the other guide surface of the second straight guide section corresponding to the unclamping angular position are connected by an arcuate connecting surface, and the center of the guide member moves along a circular arc when the guide member moves relative to the piston along the arcuate connecting surface.
Since the guide surfaces on the opposite sides of the center line of the arcuate connecting section are arcuate connecting surfaces, the center of the guide member moves along a circular arc when the guide member moves relative to the piston along either of the arcuate connecting surfaces.
Preferably, the guide groove has a semicircular cross section, the guide member is a ball capable of rolling along the guide groove, and the steel ball is supported for rotation in a bearing member.
Since the ball as the guide member rolls along the guide groove, resistance to the movement of the piston rod is relatively low.
Preferably, the piston rod turns between a first angular end position and a second angular end position, the piston rod turns from the first angular end position toward the second angular end position for normal turning and turns from the second angular end position toward the first angular end position for reverse turning, the opposite guide surfaces of the guide groove serve as a first guide surface for normal turning and a second guide surface for reverse turning, respectively, and guide the guide member so that the guide member moves relative to the piston rod along different paths in the guide groove while the piston rod turns for normal turning and reverse turning, respectively, and the first guide surface for normal turning and the second guide surface for reverse turning are formed in shapes that guide the guide member so that the guide member moves relative to the piston along a path inclined to the axis of the piston rod to convert a thrust applied to the piston rod into a torque that turns the piston rod from the first angular end position toward the second angular end position, moves relative to the piston rod along a path having a shape of a section of a sine curve or a cosine curve in a final stage of movement of the piston rod, and moves relative to the piston rod so as not to produce any torque at the second angular end position.
Preferably, the first guide surface for normal turning and the second guide surface for reverse turning are so formed that the guide member moves relative to the piston rod along a path having the shape of a section of a sine curve or a cosine curve.
Preferably, the first and the second guide surface are so formed that a tangent to the sine or the cosine curve at a turning terminating point is parallel to the axis of the piston rod and a tangent to the sine or the cosine curve at a turning starting point is inclined to the axis of the piston rod.
Preferably, the guide groove is so formed that the turning starting point on the path of the guide member for normal turning is separated axially by a distance from the turning terminating point on the path of the guide member for reverse turning, and the turning terminating point on the path of the guide member for normal turning is separated axially by a distance from the turning starting point on the path of the guide member for reverse turning.
Preferably, the piston rod turns between a first angular end position and a second angular end position, the piston rod turns from the first angular end position toward the second angular end position for normal turning and turns from the second angular end position toward the first angular end position for reverse turning, the opposite guide surfaces of the guide groove serve as a first guide surface for normal turning and a second guide surface for reverse turning, respectively, so that the guide member moves relative to the piston rod along different paths in the guide groove while the piston rod turns for normal turning and reverse turning, respectively, and the first guide surface for normal turning and the second guide surface for reverse turning are formed in shapes that guide the guide member so that the guide member moves relative to the piston rod along a path inclined to the axis of the piston rod to convert a thrust applied to the piston rod into a torque at a turning starting point, the guide member moves relative to the piston along a path that decreases gradually the torque produced by the thrust applied to the piston rod and the guide member moves relative to the piston rod so as not to produce any torque at a turning terminating point.
Preferably, in the rotary clamping cylinder actuator in which one end of the cylinder is closed by the front end cover, the piston rod connected to the piston projects to outside from the front end cover and the guide member is combined with the front end cover so as to engage in the guide groove formed in the piston rod so that the piston rod turns when the same is moved axially by the piston, the piston rod is coupled with the piston so as to be turnable relative to the piston.
Preferably, a reduced portion and a shoulder are formed in the piston rod by reducing the diameter of an end portion of the piston rod, the reduced portion of the piston rod is fitted in a center bore formed in the piston, a retaining member for retaining the piston on the reduced portion of the piston rod is attached to the extremity of the reduced portion of the piston rod so that the piston is held between the shoulder of the piston rod and the retaining member with an axial gap between the piston and the shoulder of the piston rod, and the piston rod is turnable relative to the piston.
Preferably, a gap between the reduced portion of the piston rod and a wall defining the center bore of the piston is sealed with a sealing member.
Since the diameter of the connecting portion of the piston rod is smaller than that of the piston, the piston does not turn when the piston rod turns relative to the piston. Since the resistance to the turning of the piston rod is lower than that that acts on the piston rod when the piston turns together with the piston rod. Consequently, the piston rod can be turned by applying a low working pressure to the piston.
Since the guide member is a ball and the ball is supported for rotation in the bearing member, the resistance of the guide member to the turning of the piston rod is low and hence the rotary clamping cylinder actuator can be operated by further reduced working pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a longitudinal sectional view of a rotary clamping cylinder actuator in a first embodiment of the present invention;
FIG. 2
is an enlarged cross-sectional view taken on line II—II in
FIG. 1
;
FIG. 3
is a plan view of the rotary clamping cylinder actuator shown in
FIG. 1
;
FIG. 4
is a view taken in the direction of the arrow IV in
FIG. 1
;
FIG. 5
is a development of a guide groove formed in a piston rod included in the rotary clamping cylinder actuator of
FIG. 1
;
FIGS. 6A
to
6
D are diagrammatic views for explaining actions of the rotary clamping cylinder actuator shown in
FIG. 1
;
FIGS. 7A and 7B
are diagrammatic views of modifications of the guide groove shown in
FIG. 5
;
FIG. 8
is a cross-sectional view of a rotary clamping cylinder actuator in a second embodiment of the present invention;
FIG. 9
is a development of a guide groove employed in the rotary clamping cylinder shown in
FIG. 8
;
FIG. 10
is diagrammatic view for explaining a section of a guide groove;
FIG. 11
is diagrammatic view for explaining a section of a guide groove;
FIGS. 12A
to
12
D are is a diagrammatic views for explaining actions of the rotary clamping cylinder actuator shown in
FIG. 8
;
FIG. 13
is a development of a modification of the guide groove employed in the rotary clamping cylinder actuator shown in
FIG. 8
; and
FIG. 14
is a diagrammatic view explaining effects of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to
FIG. 1
showing a rotary clamping cylinder actuator in a first embodiment of the present invention, a cylinder
1
is formed from an aluminum tube formed by an extrusion process or a cold drawing process and, as shown in
FIG. 2
, has a side wall
1
a
defining a cylinder bore
5
and provided in its outer surface with longitudinal sensor holding grooves
2
. A plurality of longitudinal through holes
3
for bolts and longitudinal holes
4
a
and
4
b
for a fluid are formed in the side wall
1
a.
When the cylinder
1
is an aluminum tube formed by an extrusion process, the cylinder bore
5
is finished in a high dimensional accuracy by a cold drawing process. Whereas the cylinder bore of a cylinder of a ferrous material or a nonmagnetic material, such as a stainless steel, must be finished by machining, the cylinder bore of a cylinder formed by a cold drawing process does not need any finishing work and hence the cylinder can be formed at low cost by a cold drawing process. The side wall
1
a
of the cylinder
1
is provided in its outer surface with a plurality of relatively wide, relatively shallow circumferential grooves
6
in addition to the sensor holding grooves
2
. The grooves
6
ensures the firm grip of the cylinder
1
by the operator, reduce the area of portions of the outer surface of the cylinder
1
in a cylinder circumscribed about the cylinder
1
to make the outer surface of the cylinder
1
not subject to damaging and improve the appearance of the cylinder
1
.
A guide member holder
7
has a flange
8
of an outside diameter equal to that of the cylinder
1
and a cylindrical holding part
10
projecting backward (downward, as viewed in
FIG. 1
) from the back surface
9
of the flange
8
and fitted in the cylinder bore
5
. The flange
8
is provided in its front surface (upper surface as viewed in
FIG. 1
) with a shallow recess
11
. The flange
8
of the guide member holder
7
is provided with through holes
12
respectively corresponding to the through holes
3
of the cylinder
1
. The guide member holder
7
is provided with a connecting passage
14
for interconnecting a first connecting port
22
a
formed in a front end cover
13
and a front chamber P
1
on the front side of a piston
43
fitted in the cylinder bore
5
, and a connecting passage
15
for interconnecting the hole
4
b
and a second connecting port
22
b
formed in the front end cover
13
.
The front end cover
13
has a hole
16
through which a piston rod
40
is extended. Since the piston rod
40
slides along the side wall of the hole
16
, the front end cover
13
is formed of an abrasion-resistant ferrous material, such as a perlitic ductile cast iron. The front end cover
13
has a substantially rectangular shape radially extending beyond the peripheral boundary of the cylinder
1
and is provided on its back surface
17
with a short boss
18
fitting in the recess
11
of the flange
8
of the guide member holder
7
. The boss
18
of the front end cover
13
and the cylindrical holding part
10
of the guide member holder
7
have the same outside diameter. A section of the back surface
17
facing the front end surface (upper end surface as viewed in
FIG. 1
) of the flange
8
of the guide member holder
7
is a sealing surface
19
. A section of the back surface
17
surrounding the sealing surface
19
is a joining surface
20
flush with the sealing surface
19
.
As shown in
FIG. 3
, a first port
21
a
and a second port
21
b
open in the side surface
13
a
of the front end cover
13
. The first port
21
a
is connected to a first passage
22
a
opening in the back end surface (lower end surface as viewed in
FIG. 1
) of the boss
18
, and the second port
21
b
is connected to a second passage
22
b
opening in the sealing surface
19
. As shown in
FIG. 4
, ports
23
a
and
23
b
connected to the ports
21
a
and
21
b
may open in the joining surface
20
. Either the ports
21
a
and
21
b
or the orts
23
a
or
23
b
may be selectively used.
The open back end (lower end as viewed in
FIG. 1
) of the cylinder
1
is covered with a back end cover
27
. As shown in
FIG. 4
, the back end cover
27
is provided with grooves
28
through which sensors
110
are inserted in the sensor holding grooves
2
, and holes
29
corresponding to the through holes
3
of the cylinder
1
. The back end cover
27
is formed by processing a drawn aluminum block. A workpiece of a predetermined thickness is cut from the drawn aluminum block, and the workpiece is machined to form a short boss
30
that is fitted in the cylinder bore
5
, a recess
31
for receiving a back end portion of the piston rod
40
, a connecting groove
32
for interconnecting a back chamber P
2
on the back side of the piston
43
and the hole
4
b,
and counterbores
33
formed around the rims of the through holes
29
. The front surface of the back end cover
27
facing the cylinder
1
is finished in a sealing surface
34
. The connecting groove
32
is formed in the boss
30
and the sealing surface
34
. Each gasket is made of a thin metal (aluminum or steel) sheet sandwiched between elastic sheets made of rubber or the like.
Gaskets
35
,
36
and
37
are sandwiched between the back surface
17
of the front end cover
13
and the guide member holder
7
, between the guide member holder
7
and the front end of the cylinder
1
and between the back end cover
27
and the back end of the cylinder
1
, respectively.
The gasket
37
sandwiched between the back end cover
27
and the cylinder
1
is provided with openings in portions thereof respectively corresponding to the sensor holding grooves
28
, the through holes
29
and the connecting groove
32
. The gasket
37
is fitted around the boss
30
. The gasket
35
sandwiched between the front end cover
13
and the guide member holder
7
is provided with openings in its portions respectively corresponding to threaded holes
24
, the second connecting passage
22
b,
the ports
23
a
and
23
b
and through holes
26
. The gasket
35
is fitted on the boss
18
and extends over the sealing surface
19
and the joining surface
20
. The gasket
36
sandwiched between the guide member holder
7
and the front end of the cylinder
1
is provided with openings in portions thereof respectively corresponding to the through holes
12
and the connecting passage
15
.
The front end cover
13
, the guide member holder
7
, the cylinder
1
, the back end cover
27
and the gaskets
35
,
36
and
37
are arranged properly, four bolts
38
are passed through the through holes
29
of the back end cover
27
, the through holes
3
of the cylinder
1
and the through holes
12
of the guide member holder
7
, and the threaded end portions of the bolts
38
are screwed in the threaded holes
24
of the front end cover
13
so as to fasten those components together to complete a cylinder unit. The joints of the component members
13
,
7
,
1
and
27
are sealed by the gaskets
35
,
36
and
37
, respectively.
The piston rod
40
extends through a hole
10
a
formed in the guide member holder
7
and the hole
16
of the front end cover
13
and a front end portion of the piston rod
40
projects forward from the front end cover
13
. A clamping arm
41
is fixedly mounted on the front end portion of the piston rod
40
. A piston support portion
42
is formed by reducing the back end portion of the piston rod
40
. The piston support portion
42
is fitted in a center bore
43
a
of the piston
43
so that the piston rod
40
is able to turn relative to the piston
43
. A magnet holding member
44
is mounted rotatably on the piston support portion
42
at a position behind the piston
43
with an annular permanent magnet
45
held between the piston
43
and the magnet holding member
44
. A bolt
46
is screwed in a threaded hole formed in the back end portion of the piston rod
40
to hold the piston
43
and the magnet holding member
44
between a shoulder
47
formed at the front end of the piston support portion
42
and a washer (retaining member)
48
fastened to the piston rod
40
with its front end surface
48
a
pressed against the back end of the piston rod
40
with the bolt
46
. The piston
43
and the magnet holding member
44
are not pressed tight against the shoulder
47
and the piston
43
and the magnet holding member
44
are able to move slightly axially between the shoulder
47
and the washer
48
. The piston
43
and the magnet holding member
44
are able to turn relative to the piston rod
40
. A gap between the piston support portion
42
and the inner circumference of the piston
43
is sealed by a sealing member
49
, such as an O-ring, fitted in an annular groove formed in the inner circumference of the piston
43
.
Referring to
FIGS. 1 and 5
, the piston rod
40
is provided in its surface with a guide groove
50
having a semicircular cross section. The guide groove
50
consists of a first straight guide section
51
, a helical or oblique guide section
52
, a second straight section
53
, a first curved connecting section
70
having the shape of a circular arc and connecting the first straight guide section
51
to the helical guide section
52
, and a second connecting section
70
having the shape of a circular arc and connecting the second straight guide section
53
to the helical section
52
. The first straight guide section
51
is formed at an angular position corresponding to an unclamping angular position B, and the second straight guide section
53
is formed at an angular position corresponding to a clamping angular position A.
When a steel ball
54
serving as a guide member moves relative to the piston rod
40
along the first straight guide section
51
or the second straight guide section
53
, the piston rod
40
moves straight at the clamping angular position A or the unclamping angular position B. When the steel ball
54
moves relative to the piston rod
40
along the helical guide section
52
, the piston rod
40
moves longitudinally and turns between the clamping angular position A and the unclamping angular position B.
The center line CL
1
of the second curved connecting section
70
is continuous with the center line CL
2
of the helical guide section
52
and the center line CL
3
of the second straight guide section
53
. The center line CL
1
is an arc of a circle having a radius R and its center at the joint P
1
of the edge line
52
a
1
of an unclamping guide surface
52
a
of the helical guide section
52
that engages the steel ball
54
when the piston rod
40
is thrust by the piston
43
toward the unclamping angular position B, and the edge line
53
a
1
of the guide surface
53
a,
i.e., a surface on the upper side of the center line CL
3
, of the second straight guide section
53
corresponding to the unclamping guide surface
52
a.
The radius R is equal to ½ of the width of the guide groove
50
.
A curved connecting surface
70
a
of the second curved connecting section
70
interconnects a clamping guide surface
52
b
of the helical guide section
52
that engages the steel ball
54
when the piston rod
40
is thrust toward the clamping angular position A, and a guide surface
53
b
of the second straight guide section
53
corresponding to the clamping guide surface
52
b.
The edge line
70
a
1
of the curved connecting surface
70
a
is an arc of a circle having a radius
2
R and its center at the joint P
1
. When the steel ball
54
moves relative to the piston rod
40
from the helical guide section
52
into the second straight guide section
53
, the curved connecting surface
70
a
guides the steel ball
54
so that the center of the steel ball
54
moves along the center line CL
1
of the second curved connecting section
70
.
Similarly, the helical guide section
52
and the first straight guide section
51
corresponding to the clamping angular position A are connected by the first curved connecting section
70
. The unclamping guide surface
52
a
that engages the steel ball
54
when the piston rod
40
is thrust toward the unclamping angular position B, and the guide surface
51
a
of the first straight guide section
51
are interconnected by a curved connecting surface
70
b
which is the same as the curved connecting surface
70
a.
Thus, the center of the steel ball
54
moves along the curved path having the shape of a circular arc when the steel ball
54
moves from the helical guide section
52
into the first straight guide section
51
corresponding to the clamping position A or the second straight guide section
53
corresponding to the unclamping position B.
The cylindrical holding part
10
of the guide member holder
7
is provided with a radial hole
53
A (FIG.
2
). A bronze bearing member
55
for supporting the steel ball
54
for rolling is fitted in the radial hole
53
A so that the steel ball engages in the guide groove
50
. When the piston
43
moves forward from its back end position shown in
FIG. 1
toward its front end position to move the piston rod
40
forward, the steel ball
54
moves relative to the piston rod
40
. In an initial stage of the forward movement of the piston
43
, the piston rod
40
holding the clamping arm
41
moves straight forward slightly. In a middle stage of the axial movement of the piston
43
, the piston rod
40
moves forward and turns from an angular position corresponding to the clamping angular position A to an angular position corresponding to the unclamping angular position B, as shown in FIG.
3
. In a final stage of the forward movement of the piston
43
, the piston rod
40
moves straight forward slightly at an angular position corresponding to the unclamping angular position B. When the piston
43
moves backward from the front end position toward the back end position, the foregoing steps of movement of the piston rod
40
are reversed.
The front end cover
13
and the back end cover
27
are fastened to the front and the back end of the cylinder
1
with the bolts
38
passed from the side of the back end cover
27
through the cylinder
1
and screwed in the threaded holes
24
of the front end cover
13
. The number of the bolts
38
may be small. Since the threaded holes
24
of the front end cover
13
are not through holes, the threaded holes
24
are not clogged with chips produced by machining even if the rotary clamping cylinder actuator is used in a vertical position with the front end cover
13
facing upward. Since the bolts
38
are extended through the through holes
3
of the cylinder
1
and the through holes
12
of the guide member holder
7
and are concealed, the rotary clamping cylinder actuator has a satisfactory appearance. The cylinder
1
is formed from a cylindrical aluminum shape originally provided with the through holes
3
in its side wall, any machining process for forming the through holes
3
is unnecessary and the cylinder
1
can be readily obtained by simply cutting the cylindrical aluminum shape in a desired length. The back end cover
27
can be easily made simply by machining an aluminum shape originally provided with the sensor holding grooves
28
and the through holes
29
.
The front end cover
13
of the rotary clamping cylinder actuator is fastened to a fixed member
100
of a machine or a jig base with bolts
101
(
FIG. 3
) passed through the through holes
26
. The gasket
35
extended over the joining surface
20
of the front end cover
13
is sandwiched between the front end cover
13
and the fixed member
100
. When a workpiece or a pallet is clamped by the clamping arm
41
of the rotary clamping cylinder actuator to machine the workpiece by a machine tool, the loosening of the bolts
101
can be prevented even if the rotary clamping cylinder actuator is vibrated because the gasket is elastic. Thus, the rotary clamping cylinder actuator clamps the workpiece with reliability. Since the back surface
17
of the front end cover
13
is covered with the gasket
35
, gaps between the ports opening in the back surface
17
and the fixed member
100
do not need to be sealed by O-rings.
The operation of the rotary clamping cylinder actuator will be described. When the rotary clamping cylinder actuator is in a clamping state shown in
FIG. 1
, the steel ball
54
is in the first straight guide section
51
of the guide groove
50
as shown in
FIG. 6A. A
working fluid is supplied into the back chamber P
2
through the second port
21
b,
the second connecting port
22
b,
the connecting passage
15
, the hole
4
b
and the connecting groove
32
. Then, the piston
43
supported on the piston rod
40
moves forward (to the left as viewed in
FIG. 6A
) and the piston rod
40
holding the clamping arm
41
clamping a workpiece W moves slightly forward as the first straight guide section
51
moves relative to the steel ball
54
.
As the piston
43
continues moving forward, the steel ball
54
moves relative to the piston rod
40
along the unclamping guide surface
52
a
of the helical guide section
52
as shown in FIG.
6
B. Consequently, the piston rod
40
advances and turns from an angular position corresponding to the clamping angular position A toward an angular position corresponding to the unclamping angular position B, the clamping arm
41
is turned from the clamping angular position A toward the unclamping angular position B. After the piston rod
40
has arrived at the angular position corresponding to the unclamping angular position B, the clamping arm
41
exerts a rotational inertial force on the piston rod
40
and the curved connecting surface
70
a
is pressed against the steel ball
54
. Thus, the steel ball
54
is guided smoothly by the curved connecting surface having the shape of a circular arc into the second straight guide section
53
corresponding to the unclamping angular position B.
Consequently, the piston rod
40
stops the turning and moves straight forward slightly as shown in
FIGS. 6C and 6D
at the angular position corresponding to the unclamping angular position B. Since the clamping arm
41
is moved straight forward after the same has been turned from the clamping angular position A to the unclamping angular position B and has been gradually stopped turning, the effect of the rotational inertial force of the clamping arm
41
on the steel balls
54
and the guide groove
50
can be moderated. The angle of turning of the piston rod
40
, hence that of the clamping arm
41
, is determined by the angular interval L between the straight guide sections
51
and
53
(FIG.
5
). The angular interval L can be accurately determined by accurately machining the piston rod
40
to form the guide groove
50
. Therefore, even if the rotary clamping cylinder actuator is assembled with an error in the stroke of the piston
43
, the angular interval L between the clamping angular position A and the unclamping angular position B remains unchanged.
In an unclamping state shown in
FIG. 6D
, the working fluid is supplied through the first port
21
a,
the first connecting passage
22
a
and the connecting passage
14
into the front chamber P
1
. Then, the foregoing unclamping steps of the rotary clamping cylinder actuator are reversed to turn the clamping arm
41
from the unclamping angular position B to the clamping angular position A. As the piston
43
continues moving backward, the steel ball
54
moves relative to the piston rod
40
along the clamping guide surface
52
b
of the helical guide section
52
. Consequently, the piston rod
40
moves backward and turns from the angular position corresponding to the unclamping angular position B toward the angular position corresponding to the clamping angular position A. After the piston rod
40
has arrived at the angular position corresponding to the clamping angular position A, the clamping arm
41
exerts a rotational inertial force on the piston rod
40
and the curved connecting surface
70
b
is pressed against the steel ball
54
. Thus, the steel ball
545
is guided smoothly by the curved connecting surface
70
b
having the shape of a circular arc into the first straight guide section
51
corresponding to the clamping angular position A. Thus, the effect of the rotational inertial force of the clamping arm
41
on the piston rod
40
and the steel ball
54
can be moderated.
Since the steel ball
54
is supported for rolling by the bronze bearing member
55
, rolling resistance to the steel ball
54
rolling along the guide groove
50
is very low, and hence the piston
43
can be moved by a low working pressure of the working fluid. The piston rod
40
can be turned relative to the piston
43
by the cooperative agency of the steel ball
54
and the guide groove
50
. Since the distance between the axis of the piston rod
40
and the outer circumference of the piston
43
is greater than that between the axis of the piston rod
40
and the inner circumference of the piston
43
, a torque produced by the resistance of the sealing member
49
a
to the turning of the piston
43
relative to the cylinder
1
is greater than that produced by the resistance of the sealing member
49
to the turning of the piston support part
42
of the piston rod
40
relative to the piston
43
. Therefore, the piston rod
40
turns relative to the piston
43
while the piston
43
does not turn relative to the cylinder, and hence a thrust to be applied to the piston rod
40
to turn the piston rod
40
is smaller than that necessary for turning the piston rod that turns together with the piston.
The center line CL
1
of each of the curved connecting sections
70
of the guide groove
50
of the piston rod
40
in this embodiment is an arc of the circle having the radius R equal to ½ of the width of the guide groove
50
. The center line CL
1
may be an arc of a circle having a radius r
1
smaller than the width of the guide groove
50
as shown in FIG.
7
A. When the unclamping guide surface
52
a
of the helical guide section
52
and the guide surface
53
a
of the second straight guide section
53
corresponding to the unclamping angular position B is connected by a curved connecting surface
70
c
(surface on the upper side of the center line CL
1
in
FIG. 7B
) having an edge line of the shape of an arc of a circle having a small radius r
2
, and the center of the steel ball
54
moves along a circular arc when the steel ball
54
rolls along the curved connecting surface
70
c,
the steel ball
54
is able to move along the curved connecting surface
70
c
and the center of the steel ball
54
is able to move along the circular arc even if the piston rod
40
cannot be turned by the inertial force of a light clamping arm in the final stage of turning of the clamping arm and the steel ball
54
cannot be guided by the curved connecting surface
70
a.
The guide groove having the shape shown in
FIG. 7B
is applicable to a clamping cylinder actuator having a clamping arm that does not move axially and only turns as disclosed in JP-B-62-5739.
The magnetic sensors
110
are held in the sensor holding grooves
2
respectively corresponding to the position of the magnet
45
held on the piston
43
when the clamping arm
41
is at the clamping angular position A to clamp the workpiece W and the position of the magnet
45
when the clamping arm
41
is at the unclamping angular position B. One of the magnetic sensors
110
detects the presence of the clamping arm
41
at the clamping angular position A as shown in
FIG. 1
to clamp the workpiece W and the other detects the presence of the clamping arm
41
at the unclamping angular position B to release the workpiece W. Since the magnet
45
supported on the piston rod
40
is spaced a long distance apart from the front end cover
13
made of a ferrous material, the intensity of a magnetic field created by the magnet
45
is not reduced by the front end cover
13
and hence the magnetic sensors
110
are able to detect the presence of the clamping arm
41
at the clamping angular position A and at the unclamping angular position B.
A rotary clamping cylinder actuator in a second embodiment according to the present invention will be described with reference to
FIGS. 8
to
14
, in which parts like or corresponding to those of the rotary clamping cylinder actuator are denoted by the same reference characters and description thereof will be omitted. Referring to
FIG. 8
, a piston rod
40
is provided in its surface with a guide groove
50
as shown in
FIG. 9
having a U-shaped cross section. The guide groove
50
has a helical or oblique guide section
51
extending at an angle to the axis CL of the piston rod
40
to turn the piston rod
40
, a first straight guide section
52
for guiding the piston rod
40
for straight movement corresponding to a clamping angular position A (first end of turning) and connected to one end of the helical guide section
51
, and a second straight guide section
53
for guiding the piston rod
40
for straight movement corresponding to an unclamping angular position B (second end of turning) and connected to the other end of the helical guide section
51
.
The guide groove
50
has opposite guide surfaces, i.e., an unclamping guide surface
57
that engages a guide pin
54
when the piston rod
40
is turned in a normal direction for unclamping and a clamping guide surface
58
that engages the guide pin
54
when the piston rod
40
is turned in a reverse direction for clamping.
A back surface
58
A
1
of a clamping guide section
58
A, with respect to the direction of thrust that causes the piston rod
40
to turn in the reverse direction is used as the clamping guide surface
58
. The clamping guide section
58
A is formed so that its center line CLA is a section of a cosine curve in the angular range of 0° to 120° as shown in
FIG. 10. A
turning terminating point Aa corresponding to the clamping angular position A on the center line CLA, corresponds to a point on the cosine curve corresponding to an angle of 0° so that a tangent to the center line CLA at the turning terminating point Aa coincides with the direction of thrust. Therefore, an axial force applied to the piston rod
40
by the guide pin
54
at the turning terminating point Aa does not produce any torque. A section of a path between a turning starting point Ba corresponding to the unclamping angular position B and a middle point is a section of the cosine curve, tangents to which are inclined to the direction of thrust. Therefore, a thrust applied to the piston rod
40
by the guide pin
54
at a point on the path between the turning starting point Ba and the middle point is converted into a torque.
As shown in
FIG. 11
, a back surface
57
A
1
of an unclamping guide section
57
A, with respect to the direction of thrust that causes the piston rod
40
to turn in the normal direction, is used as the unclamping guide surface
57
. The unclamping guide section
57
A and the clamping guide section
58
A are symmetrical with respect to an optional point. The center line CLB of the unclamping guide section
57
A is a section of a cosine curve in the range of 60° to 180°.
As shown in
FIG. 9
, in the guide groove
50
formed by combining the unclamping guide section
57
A and the clamping guide section
58
A, the turning starting end C of the center line CLB of the unclamping guide section
57
A and the turning terminating end Aa of the center line CLA of the clamping guide section
58
A are axially spaced apart, and the turning terminating end D of the center line CLB of the unclamping guide section
57
A and the turning starting end Ba of the center line CLA of the clamping guide section
58
A are axially spaced apart. When guided by the unclamping guide surface
57
(
57
A
1
), the guide pin
54
moves along a path corresponding to the center line CLB. When guided by the clamping guide surface
58
(
58
A
1
), the guide pin
54
moves along a path corresponding to the center line CLA.
As shown in
FIG. 8
, a guide member holder
7
has a holding part
10
provided with a radial hole
56
, and the guide pin
54
is fitted in the radial hole
56
.
The operation of the rotary clamping cylinder actuator will be described on an assumption that a thrust is greater than an inertial force produced by the turning clamping arm
41
. When the clamping arm
41
is at the clamping angular position A, the guide pin
54
is at the extremity of the first straight guide section
52
of the guide groove
50
as shown in FIG.
12
A. When the piston
43
supported on the piston rod
40
is moved forward (to the left as viewed in FIG.
12
A), the first straight guide section
52
corresponding to the clamping angular position A moves relative to the guide pin
54
, the piston rod
40
moves slightly forward, i.e., away from the clamping position A where the clamping arm
41
clamps the workpiece W, and the turning starting position C coincides with the guide pin
54
. As the piston
43
moves further forward, the unclamping guide surface
57
engages the guide pin
54
, and then the guide pin
54
moves relative to the piston rod
40
along a path having the shape of a section of a cosine curve having the center line CLB. Consequently, the piston rod
40
holding the clamping arm
41
moves axially turning from a position corresponding to the clamping angular position A to a position corresponding to the unclamping angular position B as shown in
FIGS. 12B and 12C
. When the piston rod
40
starts turning at the turning starting point C, the unclamping guide surface
57
is inclined at a large angle to the direction of a thrust applied to the piston rod
40
, the thrust is converted into a corresponding torque and the piston rod
40
starts turning quickly. If the path between the turning starting point C and the turning terminating point D has the shape of a section of a cosine curve in the range of 0° to 180° as shown in
FIG. 14
, torque will be produced gradually as the piston rod
40
is moved forward and the piston rod
40
will gradually start turning and, consequently, it takes a long time for the piston rod
40
to turn from the position corresponding to the clamping angular position A to the position corresponding to the unclamping angular position B.
As the turning terminating point D approaches the guide pin
54
, a rotational inertial force of the clamping arm
41
urges the piston rod
40
for movement in the unclamping direction. Since the mass of the clamping arm
41
is determined so that the thrust overcomes the inertial force, the guide pin
54
moves relative to the piston rod
40
along the unclamping guide surface
57
, i.e., along a path having the shape of a section of a cosine curve. The torque produced by the thrust decreases gradually as the piston rod
40
moves forward and the torque disappears when the turning terminating point D coincides with the guide pin
54
as shown in FIG.
12
(C). Subsequently, the guide pin
54
moves smoothly relative to the piston rod
40
from the turning terminating point D into the second straight guide section
53
and the piston rod
40
stops after moving slightly forward at the unclamping angular position B.
When the working fluid is supplied through the hole
21
a,
the first connecting passage
22
a
and the connecting passage
14
into the front chamber P
1
in a state where the piston rod
40
is at a position corresponding to the unclamping angular position B as shown in
FIG. 12D
, the clamping guide surface
58
moves along the guide pun
54
, the guide pin
54
moves relative to the piston
40
along the path represented by the center line CLA, and the clamping arm
41
is turned from the unclamping angular position B toward the clamping angular position A. First, the piston rod
40
moves slightly backward at an angular position corresponding to the unclamping angular position B, the guide pin
54
moves relative to the piston rod
40
to a position indicated by a two-dot chain line in FIG.
12
C and coinciding with the turning starting point Ba of the center line CLA of the clamping guide section
58
A. Then, the guide pin
54
moves relative to the piston rod
40
along the clamping guide surface
58
. Thus, the piston rod
40
starts turning quickly at the turning starting point Ba, the torque acting on the piston rod
40
decreases gradually as the guide pin
54
approaches the turning terminating point Aa, the torque disappears upon the arrival of the guide pin
54
at the turning terminating point Aa. Then, the guide pin
54
moves relative to the piston rod
40
along the first straight guide section
52
and the clamping arm
41
clamps a workpiece W.
Although the path of the guide pin
54
guided by the guide groove
50
between the turning starting point and the turning terminating point when the piston rod turns in the normal direction and the path of the guide pin
54
guided by the guide groove
50
between the turning starting point and the turning terminating point when the piston rod
40
turns in the reverse direction has the shape of a section of a cosine curve in the second embodiment, each of those paths may have the shape of a section of a sine curve. The clamping guide surface and the unclamping guide surface of the guide groove may be formed so that a section of the path of the guide member near the turning terminating point has the shape of a section of a sine curve or a cosine curve, and a section of the same path between the turning starting point and the turning terminating point is straight and inclined at a predetermined angle to the direction of the thrust. Although it is preferable, in view of smoothly moving the guide pin, that the path of the guide pin leading to the turning terminating point has the shape of a section of a cosine or sine curve, the path may have the shape of a successively bent line consisting of successive line segments as shown in FIG.
13
. The inclination of the successively bent center line shown in
FIG. 13
to the axis of the piston rod decreases gradually toward the turning terminating point and the line segment connected to the turning terminating point is parallel to the axis of the piston rod. Therefore, when the guide pin moves relative to the piston rod along the pass having the bent center line, the torque resulting from the thrust applied to the piston decreases gradually and disappears at the turning terminating point Aa (D). At the turning starting point Ba (C), the inclination of the bent center line to the axis of the piston rod is large and hence a thrust applied to the piston rod is converted immediately into a corresponding torque.
As apparent from the foregoing description, according to the present invention, the clamping arm turns from the clamping angular position to the unclamping angular position and moves smoothly in the axial direction at the unclamping angular position. Therefore, as compared with the guide member and the piston rod of the conventional rotary clamping cylinder actuator in which the unclamping angular position is determined by the helical guide section, the guide member and the piston rod of the rotary clamping cylinder actuator are less subject to the effect of the rotational inertial force of the clamping arm, and shocks that may be exerted on the guide member and the piston rod when the clamping arm is stopped at the unclamping angular position can be reduced. The turning angle of the clamping arm can be determined independently of the stroke of the piston.
The normal and the reverse turning of the piston rod can be quickly started at the turning starting points and hence the time necessary for turning the clamping arm can be reduced. Since the torque resulting from the thrust can be reduced to zero at the turning terminating point, the turning of the clamping arm can be very quietly stopped.
Since the distance between the axis of the piston rod and the outer circumference of the piston is greater than that between the axis of the piston rod and the inner circumference of the piston, the piston rod turns relative to the piston. The resistance to the turning of the piston rod relative to the piston is less than that to the turning of the piston rod that turns together with the piston. Therefore, the piston rod can be turned by a low working pressure applied thereto.
Although the invention has been described in its preferred embodiments with a certain degree of particularity, obviously many changes and variations are possible therein. It is therefore to be understood that the present invention may be practiced otherwise than as specifically described herein without departing form the scope thereof.
Claims
- 1. A rotary clamping cylinder, actuator comprising:a cylinder; a piston provided in the cylinder; a front end cover attached to a front end of the cylinder; a rotatable piston rod provided in an outer surface thereof with a guide groove and contained in the cylinder so as to project to outside through the front end cover and to be moved axially between a position corresponding to a clamping angular position and a position corresponding to an unclamping angular position by the piston, said piston rod being coupled to the piston so as to be turnable relative to the piston; a guide member attached to one of the cylinder and the piston and engaged in the glide groove of the piston rod so as to be movable relative to the piston rod in directions parallel to axis of the piston rod; and a clamping arm attached to a fine end of the piston rod, said clamping arm being capable of being turned together with the piston rod between the clamping angular position and the unclamping angular position; wherein the guide groove has an oblique guide section extending oblique to the axis of the piston rod to turn the piston rod, a first straight guide section connected to one end of the oblique guide section and corresponding to the clamping angular position, and a second straight guide section connected to the other end of the oblique guide section and corresponding to the unclamping angular position, and the oblique guide section and the second straight guide section are so connected that a center of the guide member moves substantially along a circular arc when the guide member moves relative to the piston rod from the oblique guide section to the second straight guide section corresponding to the unclamping angular position.
- 2. The rotary clamping cylinder actuator according to claim 1, wherein the oblique guide section and the second straight guide section corresponding to the unclamping angular position of the guide groove are connected by an arcuate connecting section having a shape of a circular arc, a clamping guide surface of the oblique guide section that engages the guide member when the piston rod is thrust by a piston toward the clamping angular position, and one guide surface of the second straight guide section corresponding to the unclamping angular position are connected by an arcuate connecting surface, and the center of the guide member moves along a circular arc when the guide member moves relative to the piston along the arcuate connecting surface in the arcuate connecting section.
- 3. The rotary clamping cylinder actuator according to claim 2, wherein, in the arcuate connecting section, an unclamping guide surface of the oblique guide section that engages the guide member when the piston rod is thrust toward the unclamping angular position by the piston, and another guide surface of the second straight guide section corresponding to the unclamping angular position are connected by an arcuate connecting surface, and the center of the guide member moves along a circular arc when the guide member moves relative to the piston rod along the arcuate connecting surface.
- 4. The rotary clamping cylinder actuator according to claim 1, wherein the guide groove has a semicircular cross section, the guide member is a ball capable of rolling along the guide groove, and the ball is supported for rolling in a bearing member.
- 5. The rotary clamping cylinder actuator according to claim 1, wherein the piston rod turns between a first angular end position and a second angular end position, the piston rod turns from the first angular end position toward the second angular end position for normal turning and turns from the second angular end position toward the first angular end position for reverse turning, and the opposite guide surfaces of the guide groove serve as a first guide surface for normal turning and a second guide surface for reverse turning, respectively, and guide the guide member so that the guide member moves relative to the piston rod along different paths in the guide groove while the piston rod turns for normal turning and reverse turning, respectively, and wherein the first guide surface for normal turning and the second guide surface for reverse turning are formed in shapes that guide the guide member so that the guide member moves relative to the piston rod along a path inclined to the axis of the piston rod to convert a thrust applied to the piston rod into a torque that turns the piston rod from the first angular end position toward the second angular end position, moves relative to the piston rod along a path having a shape of a section of a sine curve or a cosine curve in a final stage of movement of the piston rod, and moves relative to the piston rod so as not to produce any torque at the second angular end position.
- 6. The rotary clamping cylinder actuator according to claim 5, wherein the first guide surface for normal turning and the second guide surface for reverse turning are so formed that the guide member moves relative to the piston rod along a path having a shape selected from a group consisting of a section of a sine curve and a cosine curve from a turning starting point toward a turning terminating point.
- 7. The rotary clamping cylinder actuator according to claim 6, wherein the first and the second guide surface are formed such that a tangent to a curve selected from a group consisting of the sine and the cosine curve at the turning terminating point is parallel to the axis of the piston rod and a tangent to said curve selected from said group consisting of the sine and the cosine curve at the turning starting point is inclined to the axis of the piston rod.
- 8. The rotary clamping cylinder actuator according to claim 5, wherein the guide groove is so formed that the turning starting point on the path of the guide member for normal turning is separated axially by a distance from the turning terminating point on the path of the guide member for reverse turning, and the turning terminating point on the path of the guide member for normal turning is separated axially by a distance from the turning starting point on the path of the guide member for reverse turning.
- 9. The rotary clamping cylinder actuator according to claim 1, wherein the piston rod turns between a first angular end position and a second angular end position, the piston rod turns from the first angular end position toward the second angular end position for normal turning and turns from the second angular end position toward the first angular end position for reverse turning, opposite guide surfaces of the guide groove serve as a first guide surface for normal turning and a second guide surface for reverse turning, respectively, so that the guide member moves relative to the piston along different paths in the guide groove while the piston rod turns for normal turning and reverse turning, respectively, and the first guide surface for normal turning and the second guide surface for reverse turning are formed in shapes that guide the guide member so that the guide member moves along a path inclined to the axis of the piston rod to convert a thrust applied to the piston rod into a torque at a turning starting point, the guide member moves relative to the piston rod along a path that decreases gradually the torque produced by the thrust applied to the piston rod, and the guide member moves so as not to produce any torque at a turning terminating point.
- 10. The rotary clamping cylinder actuator according to claim 1, wherein a reduced portion and a shoulder are formed in the piston rod by reducing a diameter of an end portion of the piston rod, the reduced portion of the piston rod is fitted in a center bore formed in the piston, a retaining member for retaining the piston on the reduced portion of the piston rod is attached to a free end of the reduced portion of the piston rod so that the piston is retained between the shoulder of the piston rod, and the retaining member with an axial gap between the piston and the shoulder of the piston rod, and the piston rod is turnable relative to the piston.
- 11. The rotary clamping cylinder actuator according to claim 1, wherein a gap between a reduced portion of the piston rod and a wall defining the center bore of the piston is sealed with a sealing member.
- 12. The rotary clamping cylinder actuator according to claim 1, wherein a gap between the reduced portion of the piston rod and a wall defining the center bore of the piston is sealed with a sealing member.
- 13. The rotary clamping cylinder actuator according to claim 2, wherein the guide groove has a semicircular cross section, the guide member is a ball capable of rolling along the guide groove, and the ball is supported for rolling in a bearing member.
- 14. The rotary clamping cylinder actuator according to claim 3, wherein the guide groove has a semicircular cross section, the guide member is a ball capable of rolling along the guide groove, and the ball is supported for rolling in a bearing member.
- 15. The rotary clamping cylinder actuator according to claim 6, wherein the guide groove is so formed that the turning starting point on the path of the guide member for normal turning is separated axially by a distance from the turning terminating point on the path of the guide member for reverse turning, and the turning terminating point on the path of the guide member for normal turning is separated axially by a distance from the turning starting point on the path of the guide member for reverse turning.
- 16. The rotary clamping cylinder actuator according to claim 6, wherein the guide groove is so formed that the turning starting point on the path of the guide member for normal turning is separated axially by a distance from the turning terminating point on the path of the guide member for reverse turning, and the turning terminating point on the path of the guide member for normal turning is separated axially by a distance from the turning starting point on the path of the guide member for reverse turning.
- 17. The rotary clamping cylinder actuator according to claim 10, wherein a gap between the reduced portion of the piston rod and a wall defining the center bore of the piston is sealed with a sealing member.
- 18. The rotary clamping cylinder actuator according to claim 10, wherein the guide member is a steel ball, and the steel ball is supported for rolling in a bronze bearing member.
- 19. The rotary clamping cylinder actuator according to claim 11, wherein the guide member is a steel ball, and the steel ball is supported for rolling in a bronze bearing member.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-335672 |
Nov 1999 |
JP |
|
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5192058 |
VanDalsem et al. |
Mar 1993 |
A |
Foreign Referenced Citations (2)
Number |
Date |
Country |
60-123238 |
Jul 1985 |
JP |
10-315083 |
Dec 1998 |
JP |